Add an attribute to a polygon shapefile and plot it

Hello, MATLAB community!

I would like to plot an attribute of a polygon shapefile in MATLAB. The shapefile is a watershed that is divided into smaller units also known as subwatersheds.

Basically, for my analysis, I need to create a new field in the polygon, add data for each of thee subwatersheds, and plot them.

The facecolor of each subwatershed should be representative of the magnitude of the added value (higher values should be darker and lower be lighter or the other way around).

Attached is the piece of code that I wrote sometime back in MATLAB 2015a, which worked fine.

However, when I tried the same code with MATLAB 2019a, the polygon plot comes out with some white patches for few subwatersheds (attached as .jpg). I looked around but could not find the cause of this issue.

It would be great if I could get help from someone who has some experience with such an issue.

Any suggestions are appreciated. You may find the attached shapefile.

UsangShape = shaperead('testShapeFile22.shp');

for  i1 = 1:length(UsangShape) % for each subwatershed
 storeRandomData (i1,1) = randn(1);  % store the value as vector
  UsangShape(i1).newAttribute =storeRandomData (i1,1); % add data
end

ymin=floor(min(storeRandomData));
ymax=ceil(max(storeRandomData));
 
spec = makesymbolspec('Polygon', ...
                     {'newAttribute', [ymin ymax], 'Facecolor', parula})
mapshow(UsangShape, 'SymbolSpec', spec);
set(gca, 'clim', [ymin ymax],'XtickLabel',[],'YtickLabel',[],'XColor', 'none','YColor','none')
colormap(parula);
colorbar;